Touch Panel and Touch Type Input Device

ABSTRACT

A sensing apparatus that includes a polylactic acid film having a first surface and an opposing second surface. The polylactic acid film is molecularly oriented and thermally treated so as to have a shear piezoelectric property. An electrode arrangement is provided adjacent at least one of the first and second surfaces of the polylactic acid film, and is configured to detect a relative position of an input on the polylactic acid film and detect a pressure of the input toward the polylactic acid film.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of application Ser. No.13/312,098, filed Dec. 6, 2011, which is a continuation of Internationalapplication No. PCT/JP2010/058776, filed May 25, 2010, which claimspriority to Japanese Patent Application No. 2009-140287, filed Jun. 11,2009, the entire contents of each of which are incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to a touch panel and a touch type inputdevice, which are provided on e.g., a display surface and are directlytouched with a finger or are touched using an exclusive instrument bythe user to enable position information and pressed information on aplane to be inputted at the same time.

BACKGROUND OF THE INVENTION

In recent years, the number of touch type input devices, that is,devices adopting a touch panel type has been increased significantly.The number of devices which adopt the touch panel type as an inputinterface has been increased significantly together with the developmentof the thinned display technique, such as portable phones, portable gamemachines, and portable music players as well as bank ATMs and ticketvending machines in stations.

Currently used touch panels are mainly of a resistance film type and anelectrostatic capacity type, and in addition to these, there are touchpanels using an optical type, an electromagnetic induction type, andelastic surface waves with piezoelectric. Typically, these types areused to detect position information. That is, coordinate informationshowing in what position on a touch panel the user touches is obtainedto execute a designated process based on this information. As typifiedby bank ATMs, the user touches a button portion displayed on the screento be able to operate the device as if the user pressed an actual buttonfor operation. With the recent development of the graphic user interface(GUI) process technique, there are also devices in which the user cantouch the screen to scroll displayed images or can directly control agraphically displayed slide switch with a finger.

The touch panels have been required to be further varied, so that therequest to obtain pressed information together with position informationat the same time has been increased recently. That is, if binaryinformation showing in what position on the screen the user touches andhow strong the user touches the position is detected, the operabilitycan be further improved.

As a technique in connection with this, Patent Document 1 discloses atechnique in which a position detecting device is overlapped with apressure sensitive sensor to detect position information and pressedinformation at the same time.

Also, Patent Document 2 discloses a method which uses a piezoelectricfilm to obtain pressed information and detects in what portion of aplurality of electrode lines formed in a lattice shape on thepiezoelectric film a detected voltage appears to obtain positioninformation.

-   Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No.    5-61592-   Patent Document 2: Japanese Patent Application Laid-Open (JP-A) No.    2006-163618

SUMMARY OF THE INVENTION

In the touch panel described in Patent Document 1, the pressuresensitive sensor formed of a piezoelectric film or a pressure sensitiveresistor sheet is overlapped onto a typical touch panel performing onlyposition detection. The pressure sensitive sensor covers the entiresurface of the touch panel.

In general, the typical touch panel is provided on a certain imagedisplay device, and is required to have a high transparency. Each of theposition detecting touch panel and the pressure sensitive sensor has aplurality of films and electrode layers. When the films are transparentand transparent electrodes including ITO are used, the entire touchpanel can be transparent, but due to the large stacking number, thelight transmissivity is lowered. In addition, since a plurality ofcomponents and processes are necessary, the cost is increased. Further,since position information and pressed information are detectedseparately, the signal process becomes complicated.

Also, in the touch panel described in Patent Document 2, to detectposition information and pressed information at the same time, thelattice-shaped fine wire electrodes are formed with respect to thepiezoelectric film. Since position information is obtained according tofrom what lattice-shaped electrode a signal is strongly detected, allthe fine wires are required to be connected to the computationprocessing unit, with the result that the structure becomessignificantly complicated.

To address the above problems, an aspect of the present inventionprovides a touch panel which includes a molecule oriented polylacticacid film, wherein the polylactic acid film has a first principal planeand a second principal plane formed with electrodes, and the electrodeon the first principal plane includes divided electrodes which areelectrically divided into at least four.

Preferably, the electrode on the second principal plane includes dividedelectrodes formed so as to be opposite the divided electrodes on thefirst principal plane, respectively.

The electrode on the second principal plane can include a uniform groundelectrode formed so as to be equally opposite the divided electrodes onthe first principal plane.

The divided electrodes can be electrically divided by a plurality ofelectrode division lines including electrode non-forming portions, andthe electrode division lines are formed of straight lines having apredetermined width.

The electrode division lines preferably cross at one point in thesubstantially center of the polylactic acid film at a predeterminedangle. The angles formed by the electrode division lines are preferablyequal to each other.

The polylactic acid film is preferably molecule oriented by uniaxiallystretching.

The electrode division lines can be formed of a first electrode divisionline and a second electrode division line, and when an angle formed bythe first electrode division line and the stretching direction of thepolylactic acid film is θ₁ and an angle formed by the second electrodedivision line and the stretching direction of the polylactic acid filmis θ₂, the θ₁ and θ₂ satisfy the condition of the following equation 1:

−12°≦θ₁≦12°, −102°≦θ₂≦−78°  1.

The first electrode division line can be formed in the direction whichsubstantially coincides with the stretching direction of the polylacticacid film, and the second electrode division line is formed in thedirection substantially orthogonal to the first electrode division line.

Preferably, the electrodes are a transparent electrode having ZnO as amain component.

In a further aspect of the present invention, two or more polylacticacid films are stacked.

The respective divided electrodes are preferably connected to aprocessor which outputs position information and/or pressed informationbased on voltages detected independently from the divided electrodes.

The processor preferably includes at least a detection unit whichdetects respective voltages generated in the divided electrodes, astorage unit which stores a plurality of stored voltage patternsdetermined previously from respective voltages generated in the dividedelectrodes and a plurality of pieces of position informationcorresponding thereto, and a computation unit which creates a detectedvoltage pattern from the respective voltages detected by the detectionunit, compares the detected voltage pattern with the stored voltagepatterns, checks the corresponding voltage patterns with a predeterminedthreshold value to output position information, and computes pressedinformation from a predetermined voltage similarity ratio of the storedvoltage pattern and the detected voltage pattern which have beenchecked.

The molecule oriented polylactic acid film has piezoelectric properties,and has a transparency equivalent to acryl. Therefore, according to thepresent invention, the transparent electrode is provided on thepolylactic acid film, so that the touch panel and the touch type inputdevice, which have a very high transparency, can obtain, not onlyposition information, but also pressed information, at the same time,and are inexpensive can be realized.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a perspective view showing a basic structure of a touch panelof the present invention.

FIG. 2( a) is a plan view showing a front side electrode structure ofthe touch panel of the present invention, FIG. 2( b) is a plan viewshowing a back side electrode structure of the touch panel of thepresent invention, and FIG. 2( c) is a plan view showing another backside electrode structure of the touch panel of the present invention.

FIG. 3 is an explanatory view for explaining a modification by thepiezoelectric phenomenon of polylactic acid.

FIGS. 4( a) to 4(b) are perspective views for explaining a basicoperation of the present invention.

FIG. 5 is a plan view which defines coordinates for explaining the basicoperation of the present invention.

FIG. 6 is a graph showing the relation between pressed information andvoltages generated from the respective electrodes when pressing force isapplied along diagonal lines of the touch panel of the presentinvention.

FIG. 7 is a graph showing the relation between pressed information andvoltages generated from the respective electrodes when pressing force isapplied to positions at predetermined angles to an X axis at an equaldistance from the center portion of the touch panel of the presentinvention.

FIG. 8 is a graph of patterns of voltages generated from the respectiveelectrodes when predetermined pressing forces are applied topredetermined positions of the touch panel of the present invention tochange the pressing forces.

FIG. 9 is a block diagram of a touch type input device of the presentinvention.

FIG. 10( a) is a plan view showing a second example of the presentinvention, and FIG. 10( b) is a plan view showing a modification exampleof the second example of the present invention.

FIG. 11( a) is a plan view showing a third example of the presentinvention, and FIG. 11( b) is a plan view showing a modification exampleof the third example of the present invention.

FIG. 12 is a first explanatory view for explaining the third example ofthe present invention.

FIG. 13 is a first graph showing the relation between directions formedby electrode division lines and a stretching axis and voltages generatedin the respective electrodes in the touch panel shown in the thirdexample of the present invention.

FIG. 14 is a second explanatory view for explaining the third example ofthe present invention.

FIG. 15 is a second graph showing the relation between directions formedby electrode division lines and a stretching axis and voltages generatedin the respective electrodes in the touch panel shown in the thirdexample of the present invention.

FIG. 16 is a plan view showing a fourth example of the presentinvention.

FIG. 17 is a plan view showing a fifth example of the present invention.

FIG. 18 is a plan view showing a sixth example of the present invention.

FIG. 19 is an explanatory view for explaining a seventh example of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION First Example

FIG. 1 is a perspective view showing a first example. FIG. 1 enlarges atouch panel 1 which is a main configuration portion of a touch typeinput device of the present invention. The touch panel 1 is connected toa processor and forms the touch type input device of the presentinvention. The processor will be described later. The touch panel 1includes a substrate 2, the substrate 2 having both principal planesformed with electrodes. Electrodes 3 a to 3 d which are electricallydivided by electrode division lines 5 a and 5 b are formed on a firstprincipal plane of the substrate 2. The electrode division lines 5 a and5 b pass through the center of a film and cross each other at an angleof substantially 90°. The substrate 2 is structured of a polylactic acidfilm, the polylactic acid film having a stretching axis in the directionwhich substantially coincides with the longitudinal direction of theelectrode division line 5 a. In the drawing, the respective portions areexaggeratedly shown for explanation, and have dimensions different fromthe actual dimensions. In addition, here, the touch panel issubstantially square, which is not limited.

FIG. 2( a) is a plan view of the touch panel 1. An arrow 10 shows thestretching axis direction of the polylactic acid film. The arrow 10 isdepicted onto the plan view for simple explanation, but such arrow isnot depicted onto the actual touch panel 1. The electrodes 3 a to 3 dare electrically connected to a voltage detecting device, which isomitted in this drawing.

FIG. 2( b) is a plan view showing an example of a second principal plane(back side) of the touch panel 1 shown in FIG. 2( a), and reverselyshows FIG. 2( a) about an electrode division line 50 a. Electrodes 30 ato 30 d divided by the electrode division lines 50 a and 50 b are formedon the second principal plane so as to be equally opposite theelectrodes 3 a to 3 d on the first principal plane. The electrodes 30 ato 30 d are opposite the electrodes 3 a to 3 d in this order. Theelectrodes 30 a to 30 d are electrically connected to the voltagedetecting device, which is omitted in this drawing.

FIG. 2( c) is a plan view showing another example of the secondprincipal plane of the touch panel 1 shown in FIG. 2( a). A uniformelectrode 4 is formed on the second principal plane so as to be oppositeall the electrodes 3 a to 3 d on the first principal plane. Theelectrode 4 has a ground potential. The electrode 4 is electricallyconnected to the ground of the device equipped with the touch panel 1,which is omitted in this drawing.

In addition, typically, on the front side and the back side of the touchpanel, an antireflection film or a protective film is provided, or anantireflection layer or a protective layer is coated, which is omittedin this example.

Whether the electrode on the second principal plane includes the dividedelectrodes as shown in FIG. 2( b) or the uniform electrode as shown inFIG. 2( c) with respect to the electrode on the first principal plane isa design matter which can be selected as appropriate at the time ofexecution. The respective advantages will be described later.

The electrodes 3 a to 3 d, the electrodes 30 a to 30 d, and theelectrode 4 include ZnO, ITO, IZO (trademark), an inorganic electrodehaving these as a main component, or an organic electrode havingpolythiophene as a main component, and such electrodes can betransparent. However, when the electrodes are not required to betransparent, they may include a metal. Various electrode structuringmethods including deposition, sputtering, plating, and foiling areapplicable. In addition, the electrode on the first principal plane andthe electrode on the second principal plane are not always required tobe of the same type, and different types of electrodes may be used.

In particular, ZnO which enables film formation at room temperature andhas a high transparency is preferably used for polylactic acid.Originally, ZnO has the disadvantage that oxygen deficiency which is acarrier supply source is re-oxidized by reaction with moisture in theatmosphere, thereby increasing resistance. A transparent electrodeformed using an off-axis type magnetron sputtering method by doping Gawhich is an IIIB group element into ZnO at a high density of 7% byweight or more has no practical problems because the activation energyof reaction of H₂O with ZnO is increased to exhibit an excellenthumidity resistance. In addition, in the actual use, in general, on thetouch panel 1, the protective film is provided or the protective layeris coated, so that the possibility that moisture can be directlysupplied to ZnO is extremely low.

Here, the piezoelectric properties of the polylactic acid will bedescribed. The polylactic acid film is a film which is subjected tomolecule orientation and then to a thermal treatment. Typically, thepolylactic acid film is subjected to uniaxially stretching to enable thepolymer main chain to be oriented in the stretching axis direction. Thepolylactic acid is a condensation polymer of lactic acid, and the lacticacid monomer including asymmetric carbon has chirality. Therefore, thepolylactic acid includes an L type polylactic acid having a main chainwound counterclockwise, and a D type polylactic acid having a main chainwound clockwise. The former will be called PLLA, and the latter will becalled PDLA. Since PLLA is typically distributed, hereinafter, thepolylactic acid will be represented as PLLA.

In PLLA, C═O and molecules generating permanent dipoles are present inthe polymer. When the sum of the dipoles with respect to one molecularchain is calculated, the large dipole is left in the helical axisdirection. On the other hand, one reversely oriented molecule chain ispresent in each crystal unit cell of PLLA, and the dipoles are cancelledin the entire crystal. The point group of the PLLA crystal belongs toD₂, and there are d₁₄, d₂₅, and d₃₆ tensor components as piezoelectricstrain constants.

It is known that when the film is oriented by uniaxially stretching, thesymmetry of part thereof is collapsed due to the influence of thepolymer helical structure to exhibit shear piezoelectric properties. Thecomponents observed as the piezoelectric strain constants are d₁₄ andd₂₅, and the component d₃₆ is cancelled due to the presence of avertical mirror surface.

The draw ratio is preferably about 3 to 8 times. The film is subjectedto the thermal treatment after stretching to promote crystallization ofthe extended chain crystal, thereby improving the piezoelectricconstant. In the case of biaxially stretching, the draw ratio of therespective axes are made different from each other, so that the sameeffect as the uniaxially stretching can be obtained. For example, whenthe film is subjected to 8-time stretching in a certain direction as anX axis and is subjected to twice stretching in a Y axis orthogonal tothe X axis, the same piezoelectric constant effect as when the film issubjected to substantially 4-time uniaxially stretching in the X axisdirection can be obtained. Since the film which is subjected to simpleuniaxially stretching is likely to be torn along the stretching axisdirection, the film is subjected to biaxially stretching as describedabove, so that the strength can be increased to some extent.

In addition to the uniaxially stretching and the biaxially stretching,which have been described here, there is a different PLLA orientationmethod. For example, part of the side chain of the polymer issubstituted with a mesogenic group, the properties in which themesogenic group is oriented by a magnetic field or an electric field areused to orient the main chain itself in a solution, and a solvent isevaporated in this state to obtain an oriented film. Orientation is alsoenabled by applying a high pressure in the thickness direction of thefilm.

FIG. 3 is a concept diagram for explaining a modification by thepiezoelectric phenomenon of PLLA. The axis directed backward from thefront of the drawing sheet is a first axis, and the stretching axisshown by the arrow 10 is a third axis. When an electric field is appliedin the first axis direction to a PLLA film 2 a, the PLLA film 2 a isdeformed so as to be extended in the direction which substantiallycoincides with a diagonal line 12 a and to be contracted in thedirection which substantially coincides with a diagonal line 12 b due tothe influence of shear elasticity of d₁₄. Finally, the PLLA film isdeformed into a shape shown by 2 b. A symbol 11 shows the direction ofthe electric field, and shows that the electric field is presentbackward from the front of the drawing sheet. A deformation amount isexaggeratedly expressed.

It is known that in d₁₄ of PLLA, a value as much as 10 to 20 pC/N can beobtained by arranging the stretching condition, the thermal treatmentcondition, and the additive mixing condition.

In the film having such piezoelectric properties, when the electricfield is applied to cause deformation, as described above, and on thecontrary, when deformation is given, a voltage occurs. As an indexdiscussing such properties, there is a piezoelectric stress constant (gconstant). In PLLA, g₁₄ reaches 300 to 500×10⁻³ Vm/N, which is muchlarger than PVDF (g₃₁=216×10⁻³ Vm/N) and PZT (g₃₁=11×10⁻³ Vm/N).Therefore, PLLA is very preferable as sensing application.

Next, a method of obtaining position information and pressed informationusing g₁₄ of PLLA will be described.

FIG. 4( a) adds diagonal lines 13 a to 13 d for explanation to the planview of the touch panel 1 of FIG. 1. The same figure elements areindicated by the same reference symbols, and the description is omitted.When downward force is applied to the center portion of the touch panel1, the center portion of the touch panel 1 is flexed according thereto.The state of this deformation is shown in FIG. 4( b). An arrow 20 showsthe force applied to the center portion of the touch panel 1.

As understood from FIG. 4( b), all the diagonal lines 13 a to 13 d areextended substantially uniformly. FIG. 3 is applied to FIG. 4( b) forexplanation. That is, the diagonal lines 13 a and 13 c shown in FIG. 4(b) correspond to the diagonal line 12 a of FIG. 3, and the diagonallines 13 b and 13 d shown in FIG. 4( b) correspond to the diagonal line12 b of FIG. 3.

When the explanation with FIG. 3 is considered reversely, the diagonalline 12 a is extended to generate an electric field shown by the symbol11. Therefore, the diagonal lines 13 a and 13 c are extended to generateplus potentials in the electrodes 3 a and 3 c. The diagonal line 12 b iscontracted in FIG. 3, but when the diagonal line 12 b is extended, theelectric field shown by the symbol 11 is in the reverse direction.Therefore, the diagonal lines 13 b and 13 d are extended to generateminus potentials in the electrodes 3 b and 3 d.

Next, results in which a finite element method simulation is performedby using the model shown in FIG. 4( b) are shown. Table 1 showscalculation conditions, and Table 2 shows calculated results. As shownin FIG. 2( c), the electrode on the back side for this calculationincludes the uniform ground electrode.

TABLE 1 Item Conditions Film size 50 × 50 mm Film thickness 75 μmElectrode Only boundary conditions Width of electrode 0.5 mm divisionline Piezoelectric strain 2 OpC/N constant (d₁₄) Pressed spot sizeCircle having a radius of 2 mm Pressing force 0.1 N

TABLE 2 Electrode Electrode Electrode Electrode 3a 3b 3c 3d Generated78.13 −77.76 76.32 −79.39 voltage (mV)

As described above, plus potentials are generated in the electrodes 3 aand 3 c, and minus potentials are generated in the electrodes 3 b and 3d. The respective generated voltages are substantially equal.

Next, there are shown results in which coordinate axes are set so thatthe center portion of the touch panel 1 is an origin, as shown in FIG. 5and voltages generated when various positions are pressed are calculatedby using the finite element method simulation. The calculationconditions are the same as those shown in Table 1. Table 3 showsvoltages generated when positions along the diagonal line 13 a arepressed. The unit of the numerical values in the table is mV.

TABLE 3 Pressed coordinate Electrode Electrode Electrode Electrode (X,Y) 3a 3b 3c 3d (0, 0) 78.13 −77.76 76.32 −79.39 (2.5, 2.5) 81.56 −64.0042.26 −58.51 (5.0, 5.0) 85.25 −56.84 25.55 −43.18 (7.5, 7.5) 79.91−50.61 9.71 −32.61 (10.0, 10.0) 71.60 −42.06 −4.73 −20.16 (12.5, 12.5)60.59 −33.80 −7.92 −16.99 (15.0, 15.0) 41.58 −22.89 −10.55 −7.99 (17.5,17.5) 22.02 −11.44 −9.42 −3.41 (20.0, 20.0) 6.27 −3.31 −2.73 −0.57

FIG. 6 is a graph of the results of Table 3. Plot points A, B, C, and Dshown in the explanatory notes show the voltages generated in theelectrodes 3 a, 3 b, 3 c, and 3 d, respectively. It is found that thegenerated voltages are changed substantially smoothly as the pressedpositions are changed.

Table 4 shows results in which the distance from the origin of thepressed coordinates is 12.5 mm and angles formed by the Y axis to the Xaxis are changed, thereby calculating voltages generated in theelectrodes 3 a to 3 d by the finite element method simulation. Thecalculation conditions are the same as those shown in Table 1.

TABLE 4 Pressed coordinate Electrode Electrode Electrode Electrode (r,θ) 3a 3b 3c 3d (12.5, 0)  42.58 −15.54 20.47 −51.70 (12.5, 30)  71.04−36.19 6.24 −34.50 (12.5, 60)  85.46 −60.83 1.27 −25.92 (12.5, 90) 69.58 −69.53 9.28 −12.21 (12.5, 120) 59.16 −77.27 24.81 −2.84 (12.5,150) 41.53 −73.42 45.54 −4.84 (12.5, 180) 23.84 −48.71 55.84 −17.82(12.5, 210) 9.34 −32.78 69.85 −38.62 (12.5, 240) 5.05 −23.17 82.44−54.39 (12.5, 270) 13.95 −7.70 70.75 −72.37 (12.5, 300) 29.24 1.44 54.52−82.55 (12.5, 330) 48.78 −1.78 37.58 −77.54

FIG. 7 is a graph of the results of Table 4. As in FIG. 6, plot pointsA, B, C, and D shown in the explanatory notes show the voltagesgenerated in the electrodes 3 a, 3 b, 3 c, and 3 d, respectively. It isfound that the generated voltages are changed substantially smoothly asthe pressed positions are changed.

As shown in Tables 2 to 4, the voltages generated in the electrodes 3 ato 3 d are changed according to the pressed coordinates. A fixed patternis present in the signs and absolute value magnitudes of the voltagesgenerated in the respective electrodes, and the pattern is analyzed, sothat what position on the touch panel 1 is pressed can be obtained asposition information.

Next, pressing force detection method will be described. Table 5 showsresults in which generated voltages obtained when pressing forces are0.05 N, 0.1 N, and 0.2 N with respect to the respective positions of (X,Y)=(12.5, 12.5), (−12.5, 12.5), (−12.5, −12.5), and (12.5, −12.5) arecalculated by the finite element method simulation. In the respectivecoordinates, the top, middle, and bottom numerical values of thegenerated voltages in the electrodes in the table correspond to thepressing forces of 0.05 N, 0.1 N, and 0.2 N.

TABLE 5 Coordinate Pressing Electrode Electrode Electrode Electrode (X,Y) force 3a 3b 3c 3d (12.5, 12.5)  0.05N 30.29 −16.90 −3.96 −8.50 0.1N60.59 −33.80 −7.92 −16.99 0.2N 121.17 −67.60 −15.84 −33.99 (−12.5,12.5)  0.05N 15.09 −23.88 8.29 3.63 0.1N 30.17 −47.77 16.58 7.27 0.2N60.35 −95.54 33.16 14.53 (−12.5, −12.5) 0.05N −3.25 −8.28 29.73 −17.760.1N −6.50 −16.55 59.47 −35.51 0.2N −12.99 −33.11 118.93 −71.02 (12.5,−12.5) 0.05N 9.29 4.62 13.82 −25.01 0.1N 18.59 9.23 27.64 −50.02 0.2N37.17 18.47 55.27 −100.04

It is found that when the generated voltages in the respectiveelectrodes on the respective coordinates are compared, the generatedvoltages with the 0.1 N pressing force are substantially twice thegenerated voltages with the 0.05 N pressing force, and further, thegenerated voltages with the 0.2 N pressing force are substantially twicethe generated voltages with the 0.1 N pressing force.

FIG. 8 is a bar graph of the generated voltages of the respectiveelectrodes on the coordinate (12.5, 12.5) according to the pressingforces. The bar graph itself is a visualized voltage pattern. It isfound that the magnitudes of the generated voltages are shifted linearlyaccording to the pressing forces. Therefore, by the method describedhere, the magnitudes of the generated voltages are totally evaluated, sothat pressed information can be obtained. With the above description onbalance, the function of obtaining position information and pressedinformation at the same time will be described anew. FIG. 9 explains atouch type input device 100, and is a connection concept diagram of thetouch panel 1 and a processor 101. The processor 101 includes adetection unit 102, a computation unit 103, and a storage unit 104. Thedetection unit 102 is connected to the electrodes 3 a to 3 d of thetouch panel 1 by connection lines 105 a to 105 d, respectively. Thedetection unit 102 independently detects voltages generated in theelectrodes 3 a to 3 d when force is applied to the surface of the touchpanel 1.

The storage unit 104 stores, as a voltage pattern, voltages generated inthe electrodes 3 a to 3 d when a predetermined position is pressed bypredetermined pressing force. The voltage pattern includes, as unitedinformation, the signs and magnitudes of the voltages generated in theelectrodes 3 a to 3 d. As a method of storing the magnitudes of thevoltages, absolute values of the magnitudes of the voltages may bedirectly stored, and differences from or ratios to the base electrodevoltage may be stored. In particular, the storing method described heremay not be required to be limited.

Plural voltage patterns are stored, and the data may be created by asimulation or information when the touch panel 1 is actually pressed maybe directly stored. The number of voltage patterns to be previouslystored is determined as appropriate in view of the coordinate accuracyrequired of the touch type input device.

The voltages detected by the detection unit 102 are transmitted to thecomputation unit 103. The computation unit 103 generates a voltagepattern of the voltages detected by the detection unit 102 by the samemethod as the voltage patterns stored in the storage unit 104. Forexample, the voltage pattern of the detected voltages is generated bythe same method as when all the voltage patterns stored in the storageunit 104 are stored at ratios to maximum voltages generated in therespective electrodes. Next, the computation unit 103 performscomparison including signs of the created voltage pattern with thevoltage patterns stored in the storage unit 104. The voltage patternsstored in the storage unit 104 correspond to position information, butpressed information corresponding to position information is discrete tosome extent in consideration of the storage capacity limit and thecomputing speed. Therefore, the voltage patterns which coincide witheach other substantially completely cannot be obtained. When themeasured voltage pattern is compared with the stored voltage patterns,square sums of errors between the voltage ratios of the stored voltagepatterns and the measured voltage pattern are calculated, a few squaresums are selected in ascending order of magnitude, and positioninformation is assumed from magnitudes thereof. When the assumption ofposition information is completed, the computation unit 103 reads thevoltage pattern at the point located around the position from thestorage unit 104, and generates the voltage values of the electrodesgenerating the maximum voltages at the position by linear interpolation.Maximum ratios of the generated voltage values to the detected voltagesare calculated, and then, the predetermined pressing force stored in thestorage unit 104 is multiplied by each of the ratios, so that actualpressing force can be calculated. The method of determining positioninformation and pressed information described here is not limited.

As described above, in the calculation here, the electrode on the backside opposite the electrodes 3 a to 3 d includes the uniform groundelectrode 4 as shown in FIG. 2( c). The uniform ground electrode 4 has asimple structure and does not require patterning, so that the groundelectrode 4 can be formed inexpensively. In addition, the groundelectrode 4 has a back side without any electrode non-forming portions,so that when the back side is perspectively seen from the front side,the pattern of the electrode is hard to be recognized.

In addition, as shown in FIG. 2( b), when the same divided electrodes asthe front side are structured on the back side, the generated voltagesbecome larger than the former.

By the above method, the touch type input device can use the touch panel1 having a very simple structure to output position information andpressed information at the same time. As described above, PLLA used asthe material of the substrate 2 of the touch panel 1 is a condensationpolymer of lactic acid. Typically, lactic acid is made from starch withcorns as a raw material by using the force of microorganisms. Therefore,PLLA does not use a fossil fuel as a material, so that carbon dioxide inthe air cannot be increased at the time of disposal. In addition, PLLAhas a much smaller carbon dioxide exhaust amount at the time ofmanufacture than other polymers. Further, since PLLA has abiodegradability characteristic, the device having an extremely lowenvironmental load can be provided.

The position information detection and the pressed information detectionby the method described here can also be achieved by using otherpiezoelectric polymers such as PVDF as the substrate 2 in the sameelectrode structure. When PVDF is used, all the voltages generated fromthe respective electrodes have a plus potential or a minus potential.This is determined depending on the poling direction of PVDF. PLLA inwhich there is a polarity in the voltages generated in the respectiveelectrodes has a larger information amount to be obtained than PVDF. Inaddition, since PVDF is subjected to the poling process, the reductionin piezoelectric constant is observed with time, but the piezoelectricproperties of PLLA, which are caused due to the molecular orientationoccurring from the stretching and the thermal treatment, are heldsemi-permanently. Further, when PVDF which is an opaque white polymer ismade thinner, it becomes transparent, but it has a lower transparencythan PLLA, so that in view of this point, PLLA is very excellent as thetouch panel.

Second Example

FIG. 10( a) shows another embodiment of the first example shown in FIGS.1 to 2( c). FIG. 10( a) corresponds to FIG. 2( a), and the back sidescorresponding to FIGS. 2B and 2( c) are not shown. The followingexamples and modification examples are also not shown when the electrodeon the back side includes the uniform electrode. Components having thesame functions are indicated by the same reference symbols, and thedescription is omitted. The substrate 2 is rectangular. The touch panelis often provided on the surface of a display, and the number ofrectangular displays is typically overwhelmingly large, so that thetouch panel essentially has the same shape. The touch panel having suchshape can function as in the case described in the first example.

FIG. 10( b) is a modification example of the example shown in FIG. 10(a). The electrode division lines 5 a and 5 b do not pass through thecenter of the substrate 2, and a cross point thereof is in the positionshifted from the center portion of the substrate 2. When there is thebalance between the position relation between the electrodes and theconnection lines and the image displayed below, as in this example, thecross point of the electrode division lines 5 a and 5 b may be shiftedfrom the center of the substrate 2 by a predetermined amount. The crosspoint of the electrode division lines 5 a and 5 b is preferably set nearthe portion in which position detection is necessary most frequently.The shift amount may be set as appropriate according to the design bychecking the detection accuracy.

Third Example

FIG. 11( a) shows another embodiment of the second example. Componentshaving the same functions are indicated by the same reference symbols,and the description is omitted. As in the second example, the substrate2 is rectangular. PLLA of the substrate 2 is cut out so that thestretching axis is at an angle of 45° to the side of the outer frame ofthe substrate 2. As described with reference to FIG. 3, PLLA is extendedand contracted in the direction at an angle of 45° to the stretchingaxis by voltage application. Therefore, to efficiently perform voltagedetection, as shown in FIG. 11( a), preferably, one of the electrodedivision lines 5 a and 5 b is directed in the same direction as thestretching axis, and the other is directed in the direction at an angleof 90° to the stretching axis. In this case, as in FIG. 10( b), thecross point of the electrode division lines 5 a and 5 b may also beshifted from the center of the substrate 2.

FIG. 11( b) is a modification example of the example shown in FIG. 11(a). The direction of the stretching axis of PLLA of the substrate 2 isthe same as FIG. 11( a), but both the electrode division lines 5 a and 5b are not along the direction of the stretching axis, and are formedalong the diagonal lines of the substrate 2. The modification example inFIG. 11( b) can have a slightly lower detected voltage than FIG. 11( a),but can be practically used without any problems.

Next, detected voltage changes with angles formed by the stretching axisof PLLA and the electrode division lines will be described. By citingthe above description in connection with FIG. 3, a uniform electricfield is applied in the thickness direction of the PLLA film, so thatthe diagonal line 12 a at an angle of 45° to the stretching axis isextended, and the diagonal line 12 b at an angle of −45° to thestretching axis is contracted. Therefore, when the respective electrodesare arranged with respect to the stretching axis, as in the electrodepattern shown in FIG. 2( a), ideal voltage changes can be observed.

FIG. 12 shows a modification example of FIG. 2, and shows a plan viewwhen the electrode division line 5 a is rotated 45° while the orthogonalstate of the electrode division lines 5 a and 5 b of FIG. 2 is held.That is, in the drawing, θ₁=45° and θ₂=−45°. When the center portion ofthe substrate 2 is pressed in this state, as described above, a pluspotential is generated in the portion along the electrode division line5 a and a minus potential having a substantially equal absolute value isgenerated in the portion along the electrode division line 5 b.Therefore, in the electrodes 3 a to 3 d, the voltages are substantiallycanceled. Therefore, when only two electrode division lines are used,preferably, 0°≦θ₁<45° and −90°≦θ₂<−45°.

FIG. 13 is a graph showing results in which in the model shown in FIG.12, voltages generated when the center portion of the substrate 2 ispressed are calculated by the infinite element method simulation. FIG.13 shows ratios of the voltages generated in the respective electrodeswhen θ₁ is increased to 45° starting from θ₁=0° and θ₂=−90° to voltagevalues when θ₁=0° and θ₂=−90°. However, θ₂=θ₁−90°. According to thisgraph, it is found that when θ₁=45°, the generated voltages are minimum,and that when θ₁ is slightly decreased from 45°, the voltage values areincreased abruptly. When θ₁=25°, the voltages having values ofsubstantially 80% of the maximum value can be obtained. Therefore, whenθ₁ is practically set as advantageously as possible, preferably, θ₁≦25°.In this graph, the voltage values are symmetric with respect to θ₁=0°,so that the range of θ₁ may be −25°≦θ≦25°.

Next, the case that the relation in which θ₂=θ₁−90° is not satisfiedwill be described. FIG. 14 shows a modification example of FIG. 2 and aplan view when the electrode division line 5 a is rotated θ₁ from thestretching axis and the electrode division line 5 b is rotated θ₂ fromthe stretching axis.

FIG. 15 is a graph showing results in which in the model shown in FIG.14, voltages generated when the center portion of the substrate 2 ispressed are calculated by the finite element method simulation. FIG. 15shows ratios of voltages generated in the respective electrodes when θ₁is increased to 30° starting from θ₁=0° and θ₂=−90° to voltage valueswhen θ₁=0° and θ₂=−90°. However, θ₂=−θ₁−90°. According to this graph, itis found that the voltages in the divided electrodes 3 a and 3 c areincreased gradually, and the voltages in the divided electrodes 3 b and3 d are decreased gradually. The decreasing rate of the voltages in thedivided electrodes 3 b and 3 d is larger than the increasing rate of thevoltages in the divided electrodes 3 a and 3 c. When the voltage havinga value of 80% of the maximum value is attempted to be obtained, therange of θ₁ is 0°≦θ₁≦12°. In this graph, the voltage values aresubstantially symmetric with respect to θ₁=0°, the range of θ₁ may be−12°≦θ₁≦12°. As described with reference to FIGS. 12 and 13, when therelation of θ₂=θ₁−90°, the range of θ₁ is −25°≦θ₁≦25°, so that thevoltage of 80% or more of the maximum value of the generated voltage canbe detected. Therefore, with all things considered, when −12°≦θ₁≦12°, θ₂is in the range of −102°≦θ₂≦−78°, so that the practically preferablerange can be determined without setting any special relation between θ₁and θ₂. Here, the decreasing amount of the voltage with respect to themaximum voltage is 80%, but this is an amount which can be typicallyconsidered by those skilled in the art, and the decreasing amount may beconsidered to be a smaller value than this when there are no problems inthe actual use, and the values of θ₁ and θ₂ to be taken may be increasedas appropriate.

Fourth Example

FIG. 16 is a plan view showing another embodiment of the first to thirdexamples. Components having the same functions as the above examples areindicated by the same reference symbols, and the description is omitted.The electrode formed on the principal plane of the substrate 2 isdivided into eight divided electrodes 3 a to 3 h by the electrodedivision lines 5 a to 5 d. The operation principle of this example isequal to that described in the first example.

The number of voltage detection elements is increased, so that thevoltage pattern with respect to position information can be formed morefinely. Thereby, both position information and pressed information canincrease the accuracy.

All the electrode division lines 5 a to 5 d cross in the center portionof the substrate 2 in this example, but are not always required to crossin the center portion, as described in the second example.

Preferably, the electrode division lines are in the direction whichcoincides with the stretching axis and are orthogonal thereto, or otherelectrode division lines are set at angles as described in the thirdexample so that the angles formed by the electrode division lines areequalized, or other electrode division lines are provided so that thedivided electrodes divided by the electrode division lines are dividedby an equal area to the extent possible.

Fifth Example

FIG. 17 is a plan view showing a further embodiment of the first tofourth examples. Components having the same functions as the aboveexamples are indicated by the same reference symbols, and thedescription is omitted. Irregular shaped electrodes 3 a to 3 d andelectrode non-forming regions 8 a to 8 g are formed on the principalplane of the substrate 2. The electrodes 3 a to 3 d are electricallydivided by the electrode non-forming regions, and can perform the sameoperation as other examples. Centerlines 31 a to 31 d are thecenterlines showing the longer axis of the electrodes. As shown here,the electrodes are not always required to cover the entire principalplane of the substrate 2. In the electrode structure shown in FIG. 17,each of the electrodes 3 a to 3 d is in the direction at one of 45° and−45° to the stretching axis shown by the arrow 10, that is, each of thecenterlines 31 a to 31 d is in the direction at one of 45° and −45° tothe stretching axis shown by the arrow 10, so that the possibility thatonly electric charges of the same sign can occur in the island of oneelectrode by pressing becomes extremely high. Therefore, the possibilitythat the voltages can be cancelled by reverse electric charges becomesvery low.

The electrodes are not always required to be axisymmetric with respectto the centerlines of the substrate 2. The methods shown in the secondand fourth examples are combined to enable various electrode shapes tobe set. The edges of the electrodes are not always required to be astraight line, and may be a curved line. These are matters determined,as need, according to the design.

Sixth Example

FIG. 18 is a plan view showing an embodiment having an electrode shapeconcept different from the first to fifth examples. Electrodes 9 a to 9t are formed in a check pattern on the principal plane of the substrate2. All the extraction electrodes of the electrodes 9 a to 9 t are notshown. Pressing force is applied to a predetermined position on thesubstrate 2, so that voltages according to the pressed coordinate andthe pressing force are generated in the electrodes 9 a to 9 t. Since aplurality of electrodes are present, a detailed voltage pattern can beobtained, so that the improvement of the position detection accuracy canbe expected. Since the number of voltages obtained is large to increasethe load of the analyzing process, the computing process may be executedby narrowing down the electrodes which output voltages above a specifiedthreshold value.

When the number of divided electrodes is increased as in the exampleshown here, the consideration of the direction with the stretching axisbecomes meaningless, so that free arrangement is enabled. Here, theexample in which the electrodes are arranged in the check pattern, butthe electrodes may be arranged in a matrix sectioned by lattice-shapedelectrode division lines. In the lattice-shaped electrode division linesat this time, more preferably, one of the vertical axis and thehorizontal axis is along the stretching axis and the other is atsubstantially 90° with respect to the one axis.

In addition, the shape of the electrodes is not limited to be square andrectangular, and may be polygonal, circular, elliptical, and irregularshape. The same position information and pressed information obtainingmethod as the first example is used. The electrode division number is adesign matter to be determined in consideration of the signal processingability.

As described in the first example, the electrode on the back side in thesecond to sixth examples may include the divided electrodes opposite theelectrodes shown in the plan views in the examples, and may form auniform ground electrode. This is a design matter which can be selectedas appropriate for execution.

The case that the number of divided electrodes is reduced to less thanfour will be described here. For example, when the electrode formed onthe principal plane is divided into two, the detected voltage pattern issignificantly deteriorated, with the result that the detection ofposition information can be rough. Various accuracies are required ofthe touch panel according to devices to which the touch panel isapplied, so that among the devices, the devices requiring only lowaccuracy can reduce the electrode division number. For example, onlywhen which of the right half and the left half of the touch panel ispressed should be judged, the electrode division number may be about twoor three.

Seventh Example

FIG. 19 is a concept diagram for explaining a still further embodiment.In the substrate 2, two PLLA films 201 a and 201 b are stacked. The PLLAfilms 201 a and 201 b are formed with electrodes as described in theabove examples. The adhesive interface portion of the PLLA films 201 aand 201 b is on the ground electrode side of both films, which is simpleand preferable in structure. In this drawing, the electrodes and theadhesive are omitted. FIG. 19 shows a cross section of the portion towhich a stress shown by the arrow 20 is applied, and the substrate 2 isflexed by this stress. With the interface as a neutral surface, acompressive stress occurs in the PLLA film 201 a, and a tension stressoccurs in the PLLA film 201 b. When the four divided electrodes areformed on the PLLA films 201 a and 201 b, voltages according to thestresses are generated in the electrodes. Since the PLLA films 201 a and201 b can form a more detailed voltage pattern than one layer, positioninformation and pressed information can both increase the accuracy.Also, when the angle formed by the stretching directions of the PLLAfilms 201 a and 201 b is 90°, molecular chains are perspectively formedin a lattice shape, so that the touch panel can be strong. However, theangle between the stretching axes is not necessary 90°, and when it islarger than 0°, the increase of the strength can be expected. Also, thestacking number is not limited to two, and may be increased, as needed.The touch panels shown in the first to fifth examples only show typicalexamples of the present invention. The results calculated by the finiteelement method simulation are changed according to film thickness, otherelectric constants, the types, thickness, and hardness of protectivefilms to be stacked, and the numerical values shown here are notlimited. Therefore, the distribution, detection method, and computingmethod of detected voltages should be determined according to the designfor execution.

The touch panel and the touch type input device of the present inventioncan obtain position information and pressed information at the same timeby a simple structure, have a high transparency, and can be inexpensive.Further, a very great merit that no load is given to an environment atthe time of disposal can be obtained, so that there is an industrialapplicability.

DESCRIPTION OF REFERENCE SYMBOLS

-   -   1 Touch panel    -   2 Substrate    -   3 a to 3 h Divided electrode    -   4 Ground electrode    -   5 a to 5 d Electrode division line    -   8 a to 8 g Electrode non-forming portion    -   9 a to 9 t Electrode    -   10 Arrow showing the stretching axis of a film    -   11 Symbol showing the direction of an electric field    -   30 a to 30 d Electrode    -   31 a to 31 d Electrode centerline    -   50 a, 50 b Electrode division line    -   100 Touch type input device    -   101 Processing unit    -   201, 201 b PLLA film

1. A sensing apparatus comprising: a polylactic acid film having a firstsurface and an opposing second surface, the polylactic acid film beingmolecularly oriented and thermally treated so as to have a shearpiezoelectric property; and an electrode arrangement adjacent at leastone of the first and second surfaces of the polylactic acid film, theelectrode arrangement being configured to detect a relative position ofan input on the polylactic acid film and detect a pressure of the inputtoward the polylactic acid film.
 2. The sensing device according toclaim 1, wherein the polylactic acid film is an L type polylactic acidfilm.
 3. The sensing device according to claim 1, wherein the polylacticacid film is a D type polylactic acid film.
 4. The sensing deviceaccording to claim 1, wherein the electrode arrangement comprises: adivided electrode on the first surface of the polylactic acid film, thedivided electrode being electrically divided into at least foursections; and an electrode on the opposing second surface.
 5. Thesensing device according to claim 4, wherein the electrode on theopposing second surface of the polylactic acid film is a dividedelectrode having respective sections opposite to the sections of thedivided electrode on the first surface of the polylactic acid film. 6.The sensing device according to claim 4, wherein the electrode on theopposing second surface of the polylactic acid film is a uniform groundelectrode arranged opposite to the divided electrode on the firstsurface of the polylactic acid film.
 7. The sensing device according toclaim 4, wherein the divided electrode is electrically divided by aplurality of electrode division lines including electrode non-formingportions.
 8. The sensing device according to claim 7, wherein theelectrode division lines are straight lines having a predeterminedwidth.
 9. The sensing device according to claim 7, wherein the electrodedivision lines cross at a point in substantially a center of thepolylactic acid film at predetermined angles.
 10. The sensing deviceaccording to claim 9, wherein the predetermined angles formed by theelectrode division lines are equal to each other.
 11. The sensing deviceaccording to claim 7, wherein the plurality of electrode division linesinclude at least a first electrode division line and a second electrodedivision line, wherein when a first angle formed by the first electrodedivision line and a stretching direction of the polylactic acid film isθ₁ and a second angle formed by the second electrode division line andthe stretching direction of the polylactic acid film is θ₂, and θ₁ andθ₂ satisfy:−12°≦θ₁≦12°, −102°≦θ₂≦−78°.
 12. The sensing device according to claim11, wherein the first electrode division line is in a direction whichsubstantially coincides with the stretching direction of the polylacticacid film, wherein the second electrode division line is in a directionsubstantially orthogonal to the first electrode division line.
 13. Thesensing device according to claim 4, wherein at least one of the dividedelectrode on the first surface of the polylactic acid film and theelectrode on the opposing second surface of the polylactic acid film isa transparent electrode having ZnO as a main component.
 14. The sensingdevice according to claim 1, wherein the polylactic acid film includestwo or more stacked polylactic acid films.
 15. A touch type input devicecomprising: the sensing device according to claim 1; and a processorconnected to the electrode arrangement, the processor configured tooutput at least one of position information and pressed informationbased on voltages detected from the electrode arrangement.
 16. The touchtype input device according to claim 15, wherein the processor includesat least: a detection unit which detects voltages generated in portionsof the electrode arrangement; a storage unit which stores a plurality ofstored voltage patterns determined previously from the voltagesgenerated in the portions of the electrode arrangement and a pluralityof pieces of position information corresponding thereto; and acomputation unit which creates a detected voltage pattern from thevoltages detected by the detection unit, compares the detected voltagepattern with the stored voltage patterns, checks the correspondingvoltage patterns with a predetermined threshold value to output theposition information, and computes the pressed information from apredetermined voltage similarity ratio of the stored voltage pattern andthe detected voltage pattern which have been checked.
 17. A touch typeinput device comprising: the sensing device according to claim 4; and aprocessor connected to the sections of the divided electrode, theprocessor configured to output at least one of position information andpressed information based on voltages detected independently from thesections of the divided electrode.
 18. The touch type input deviceaccording to claim 17, wherein the processor includes at least: adetection unit which detects respective voltages generated in thesections of the divided electrode; a storage unit which stores aplurality of stored voltage patterns determined previously from therespective voltages generated in the sections of the divided electrodeand a plurality of pieces of position information corresponding thereto;and a computation unit which creates a detected voltage pattern from therespective voltages detected by the detection unit, compares thedetected voltage pattern with the stored voltage patterns, checks thecorresponding voltage patterns with a predetermined threshold value tooutput the position information, and computes the pressed informationfrom a predetermined voltage similarity ratio of the stored voltagepattern and the detected voltage pattern which have been checked.